Changes of Renal Resistive Index in Critically Ill Patients Undergoing Continuous Renal Replacement Therapy - Observational Study.

A significant number of critically ill patients experience acute kidney injury (AKI), an independent factor contributing to increased mortality. Prevention of AKI and monitoring kidney function are crucial. Commonly used markers such as serum creatinine and hourly diuresis are employed to assess AKI severity, but they are not ideal due to their late elevation in the disease course. Therefore, alternative methods for detecting and evaluating kidney dysfunction at an earlier stage are sought.

Previous studies have demonstrated a correlation between the risk of AKI and the resistive index of renal parenchymal arteries. Renal resistive index (RRI) is a parameter calculated from Doppler measurements, representing the difference between peak blood velocity during systole and end-diastolic velocity divided by peak systolic velocity [(Vs-Vd) /Vs]. In healthy adult kidneys, the RI typically ranges from 0.6 to 0.7. Changes in RRI can be observed much earlier than an increase in serum creatinine concentration and/or a decrease in hourly diuresis.

Some patients with acute kidney injury require renal replacement therapy. Continuous renal replacement therapy (CRRT) is commonly used in critically ill patients, causing less circulatory destabilization compared to intermittent therapies. However, adverse effects accompany renal replacement therapies, including thromboembolic complications, bleeding, infections, blood cell damage, altered drug pharmacokinetics, and loss of proteins and vitamins.

In addition to determining the appropriate initiation time for CRRT, identifying the optimal moment to end the treatment is crucial. CRRT is typically applied for several days, and during the procedure, it is challenging to ascertain whether renal function has improved and whether CRRT can be safely discontinued. The hypothesis is that there may be a correlation between changes in RRI and the recovery of kidney function. This may enable the early identification of patients who have regained kidney function, allowing for the earlier termination of CRRT.

In 1989, a study was conducted on children undergoing peritoneal dialysis due to AKI, showing a relationship between a decrease in RRI and the restoration of kidney function. However, no similar study has been conducted on adult patients undergoing continuous renal replacement therapy.